Metal conditioning bath comprising sodium hydroxide,nitric acid,and gum arabic



United States Patent 3,425,854 METAL CONDITIONING BATH COMPRISING SODIUMHYDROXIDE, NITRIC ACID, AND GUM ARABIC Kern C. Borden, 4368 71st St., LaMesa, 'Calif. 92041 No Drawing. Filed May 2, 1966, Ser. No. 546,579 U.S.Cl. 106208 9 Claims Int. Cl. C09k 3/00; C231 1/08 ABSTRACT OF THEDISCLOSURE A method of and a bath for conditioning a photographic metalplate prior to the application of a presensitizer to the plate, the bathincluding a solution of sodium hydroxide, nitric acid, water soluble gumarabic and water.

The present invention relates to a bath for conditioning metal surfaces.More particularly it relates to a method of and a bath for chemicallyconditioning metal surfaces for application of the sensitizer used inphotoengraving processes.

The bath of this invention comprises an alkali including substantially8.3 by weight of sodium hydroxide, an acid including substantially 1% byweight of nitric acid, substantially 7% by weight of Water solubleprotective coating agent, and substantially 83.7% by weight of water.

Other features and the advantages of the present invention will beapparent from the following description.

In the process of photoengraving, a sensitizer is applied to a sheet ofmetal and the negative of the positive to be printed is printed on thesensitizer. The metal surface must be conditioned for the sensitizer andthis conditioning is generally accomplished by a mechanical rougheningof the surface, such as by buffing said surface.

The metal conditioning bath of this invention may be prepared in manyways, but the following procedure and commercial chemicals arepreferred. A sodium hydroxide mixture is formed by mixing enough sodiumhydroxide flake technical, 50% liquid solution, to comprise 10.9% byWeight of the final solution with enough water to comprise 25% by weightof the final solution.

A nitric acid mixture is formed by mixing enough nitric acid, technicalgrade, 42 degrees Baum, to comprise 1.6% by weight of the final solutionwith enough water to comprise 23.4% by weight of the final solution.

The nitric acid mixture is then mixed with the sodium hydroxide mixture.A water soluble protective coating agent, such as gum arabic or karyo isthen added. Preferably enough gum arabic, 14 degrees Baum, to comprise7.1% by weight of the final solution is then mixed with the nitricacid-sodium hydroxide mixture. Water is added to the resulting mixtureto make up the remaining 30% of the bath solution. The final solutionshould be agitated sufiiciently to assure a complete mix.

The metal conditioning bath may then be applied to the metal surfaceprepared for sensitizing and application may be accomplished by eitherdipping the metal in the bath or by wiping or brushing the bath on themetal surface. The bath is preferably brushed on the metal surface by acoir bristle scrub brush. The bath is brushed across the surface in onedirection and then across the same surface in the opposite direction.

3,425,854 Patented Feb. 4, 1969 ice During this application, the met-a1will be observed to turn from a shiny surface to a dull, cloudy,non-reflecting surface. If there are any resistant spots, there may bereapplication to these areas to effect the non-reflective finish.

Application of this conditioning bath in the above described mannercauses the metal surface to grain, thus becoming roughened and preparedfor application of the sensitizer. The gum arabic protective coatingagent protects the surface from the atmosphere during the chemicalreaction. After the metal has become grained, the bath should then bethoroughly rinsed from the surface by water and the surface wiped cleanwith a sponge or cotton cloth. When zinc or magnesium plates are beingprepared, the chemical reaction time is only five to ten seconds and thebath may be washed from the surface after that time.

From the foregoing it will be apparent that the bath of this inventionprovides a convenient, economic and rapid means for preparing metalsurface for application of photoengraving sensitizers.

While the form of embodiment herein described constitutes a preferredform, it is understood that other forms may be adopted falling withinthe scope of the claims that follow.

I claim:

1. A bath for conditioning a photographic metal plate prior to theapplication of a presensitizing agent to the plate, which bath comprisesby weight:

(A) an alkali including substantially 8.3% NAOH;

(B) an acid including substantially 1% HNO (C) substantially 7% watersoluble gum arabic;

(D) substantially 83.7% H 0.

2. A bath as defined in claim 1, characterized in that said alkali (A)is hydroxide flake technical, 50% liquid solution.

3. A bath as defined in claim 1, characterized in that said acid (B) isnitric acid, technical grade, 42 degrees Baum.

4. A bath as defined in claim 1', characterized in that the gum arabicis grade at 14 degrees Baum.

5. The steps in the method of conditioning a photographic metal plateprior to the application of a presensitizer to the plate, which stepscomprise:

(A) preparing a solution containing the following by weight:

(1) an alkali including 8.3% sodium hydroxide, (2) an acid including 1%nitric acid, (3) a 7% water soluble gum arabic, (4) 83.7% water;

(B) applying the combined solution to the plate;

(C) thereafter rinsing the plate.

6. The steps in the method as defined in claim 5, characterized in thatthe application of the combined solution to the plate is by brushingsaid combined solution on the plate.

7. The steps in the method as defined in claim 5, characterized in thatthe application of the combined solution to the plate is by brushingsaid combined solution on the plate first on one direction and then inthe other.

8. The steps in the method as defined in claim 5, characterized in thatthe application of the combined solution is by dipping the plate in saidcombined solution.

9. The steps in the method as defined in claim 5, characterized in thatthe application is continued until the surface of the metal plate beingtreated becomes nonreflective.

References Cited UNITED STATES PATENTS Tanner et a1 1486.15 Wood et a1101465 Fink 1486.14

Griffith 1062 Whyzmuzis 106208 Cohn 9633 4 OTHER REFERENCES Roy L.Whistler, Industrial Gums, 1959, pages 243- 245.

5 JULIUS FROME, Primary Examiner.

T. MORRIS, Assistant Examiner.

US. Cl. X.R.

